Glomus tumours are neoplasms which resemble elements of the glomus apparatus of the skin. The glomus apparatus contains a central coiled canal, the Sucquet-Hoyer canal, which is lined by endothelium and several layers of glomus cells. Glomus tumours combine cells resembling glomus cells and vascular structures.

Clinically, the glomus tumour is almost always a solitary, purple dermal nodule on the extremities, particularly the fingers and toes. It may have a subungual location and lie within a slight depression in the underlying phalanx. This variant usually presents in adults and occurs with an equal sex incidence. The tumours are often painful, although with variable intensity, but may be severe and paroxysmal; pain can occur spontaneously or be induced by pressure or cold. Rarely, a small cluster of tumours may occur. Although they almost always occur in the skin, rare lesions have been reported at other sites, including the deep soft tissues, bone, vagina, trachea, lung, GI tract, oral cavity, nasal cavity, within veins, and in cutaneous nerves.

The glomus tumour proper is a well-circumscrubed or encapsulated dermal tumour which may extend into the subcutis. It is composed of solid aggregates of glomus cells surrounding inconspicuous vessels. Glomus cells are rounded, regular cells with eosinophilic cytoplasm and darkly staining round to oval nuclei. Tumour cells and vessels are embedded in a fibrous stroma. Some tumours contain large amounts of myxoid stroma. The uniformity of the cells and their lack of pleomorphism are features of these tumours.

Atypical, infiltrative, malignant, and symplastic glomus tumours have also been described.